What's the ideal climate for walnut trees?
Written by
Liu Xiaohui
Reviewed by
Prof. Charles Hartman, Ph.D.Walnut trees need very specific climate conditions for them to thrive. I had a Carpathian walnut growing in Montana that survived winters down to -25°F, but it did die during the humid summers of Georgia. They thrive in USDA zones 3-9 where cold dormancy breaks buds and summer heat plumps and fills kernels. They also should not be planted in areas with coastal fog, as these are good areas for fungal diseases to thrive.
Temperature Ranges
- Winter chill: 400-1,500 hours below 45°F (7°C)
- Summer heat: 75-85°F (24-29°C) for kernel development
- Avoid regions with temperatures above 100°F (38°C) for extended periods
Frost-Free Period
- 140+ days between last spring frost and first fall frost
- Late spring frosts damage new growth
- Plant on slopes to reduce frost pocket risks
Seasonal Challenges
- Humidity: Promotes blight in English walnuts
- Dry winds: Desiccate leaves in arid zones
- Late rains: Cause pre-harvest mold in black walnuts
Microclimates preserve marginal areas for growing. By planting black walnuts on the north slope of my farm, I delayed budding in the spring to avoid frost damage. Similarly, plantings that face south can potentially be used in cooler areas to increase summer heat accumulation. Always choose varieties that match your frost date and summer heat units.
Be aware of soil moisture levels and weather conditions. My orchard in Oregon utilizes windbreaks to reduce the drying effect of coastal winds. If you reside in a dry area, you are likely using a drip irrigation system to make up for low rainfall. It is always good practice to install weather stations for monitoring chill hours and use smartphone applications like FarmLogs to help predict your bloom times, and even harvest times for those fruit varieties with a longer cycle.
Read the full article: How to Grow Walnuts: 7 Essential Steps for Healthy Trees
